Opalized wood is a fossilized material formed when silica-rich fluids replace organic wood tissues with opal or chalcedony while preserving the internal cellular structure. Collectors look for visible annual rings, bark textures, and vibrant internal colors caused by trace metal inclusions. It is most commonly found in sedimentary layers where ancient volcanic ash or groundwater provided high concentrations of silica.
Is this opalized wood?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch opalized wood with a known reference. Opalized Wood sits at Mohs 5.5-6.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Opalized Wood leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Opalized Wood typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: brown, red, yellow, white, black, multicolored.
- 5Look at form & habitCrystal system: amorphous. Typical habit: pseudomorph.
Often confused with
Opalized Wood vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Opalized Wood and waxy on Agate.
How to tell apart: Luster reads vitreous on Opalized Wood and waxy on Jasper.
How to tell apart: Luster reads vitreous on Opalized Wood and waxy on Chalcedony.
Often found alongside opalized wood
Minerals reported to co-occur with opalized wood. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 5.5-6.5
- Density
- 2.0-2.5 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Amorphous
- Crystal habit
- Pseudomorph
- Cleavage
- None
- Fluorescence
- Often None, Can Be Weak Green Under SW UV
- Rarity
- Common
- Uses
- Lapidary, Decorative, Collector
- Host rock
- Sedimentary Deposits
- Typical price
- $5-50 for small specimens, $100-500+ for large polished displays
Where rockhounds find opalized wood
54 mapped spotsClassic worldwide localities
- Arizona, USA
- Madagascar
- Oregon, USA
- Indonesia
- Argentina
U.S. states with opalized wood
Each link opens a state-specific list of mapped rockhounding spots that produce opalized wood.
Field-hunting tip
Look in sedimentary deposits country — that is the host setting where opalized wood typically forms. If you start seeing quartz, chalcedony, jasper in float, you are in the right ground. Field specimens usually show a pseudomorph habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Nebraska, Washington, Idaho — start trip planning there.
Common questions
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Find opalized wood on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
